The American Civil Liberties Union released records on Feb. 22 that start to reveal the scope of secret cell phone surveillance by law enforcement agencies in Florida.

Cell site simulators, known as StingRay, have become increasingly popular among Florida law enforcement agencies. The technology fools a cell phone into thinking it is communicating with a service tower. The cell phone then sends location and other data to law enforcement agencies, allowing police to track someone’s movements. This type of surveillance does not require a warrant or probable cause.

The use of StingRay technology started in Florida as early as 2006. A Palm Bay Police Department investigation used StingRay to track a suspect, without asking the court for a warrant or any sort of authorization. Instead, Palm Bay police called up Harris Corporation, whose office is nearby, for technical assistance.

The Orange County Sheriff’s Office conducted 558 investigations from 2008 to 2014 in which StingRay technology may have been used.

The Miami-Dade Police Department used StingRay in 59 closed criminal cases during a one-year period ending in May 2014.

Federal officials have struggled to keep information about StingRay secret in Florida, whose public records law allows for the disclosure of more law enforcement information than in other states. The FBI has been asking law enforcement agencies to sign non-disclosure agreements. In denying the ACLU’s records request, the Brevard Sheriff’s Office cited such an agreement with a “federal agency.” The U.S. Marshals Service went as far as to seize StingRay records from the Sarasota Police Department in order to prevent their disclosure to the ACLU.